Retail operates on a very predictable cyclical schedule. If you know exactly when new inventory hits the floor, you know exactly when the old inventory goes on massive clearance.
For example, buy your winter coats in March and your patio furniture in September. You might have to store it for a few months, but you'll pay a fraction of the seasonal price.
Electronics are best purchased in November, while gym memberships and fitness equipment always see their best promotions in the first two weeks of January.